The invention relates to the manufacture of tires and more precisely to a molding process and to a molding device.
Many ways have been developed for attenuating the noise generated by tires during running. This noise is mainly generated by contact between the tread and the ground, but also by the vibration of the air inside the tire. This particular noise is also called “cavity noise”.
To reduce cavity noise, novel solutions have been proposed such as the use of foam, the fitting of resonators of the Helmholtz resonator type, or the provision of obstacles to the propagation of soundwaves on the internal surface of the tire.
These obstacles may consist of a multitude of elements oriented in the radial direction, which takes the form of elongate protuberances, of small size and small cross sections, and which may have a tapered end.
These elements may be fastened to the inner wall, or just simply molded during the step of molding and vulcanizing the tire.
A tire of this type has been described, for example in the Japanese Publication 2006-117115. This publication also discloses a manufacturing process for producing this type of tire.
This process consists in molding the protuberances during the operation of vulcanizing the tire. For this purpose, a rigid core is introduced into the internal space of the tire blank in such a way that said core occupies the entire internal space for the purpose of transmitting, by contact with the internal wall, the pressure and the heat needed for molding and vulcanizing. This core comprises perforations of small cross section opening radially into circumferential ducts intended for removing the air.
Upon introducing the core and the tire blank into the mold, the pressure exerted by the core on the constituent material of the internal wall of the tire causes said material to be transferred by flowing into the perforations made in the rigid core. The occluded air is removed via the circumferential ducts. Vulcanization of the tire takes place at the same time as the vulcanization of the protuberances, which thus take the form of perforations made in the core.
However, the implementation of this process and the use of the device that are described in this publication require equipment specific to the use of rigid cores and a curing press suitable for accommodating this type of core.